When you talk in political circles about an Iowa endurance test, a reference to the presidential caucuses looming in a dozen days is unmistakable. Use the phrase at the Capitol, though, and the meaning may point elsewhere.

Charles E. Grassley, with his inimitable personality blend that’s equal parts cantankerous and friendly independent-mindedness, manages to avoid spending too much time in fundraising call rooms, hearing the pleadings of lobbyists or dropping by charity dinners

. (He’s steadfastly resisted a blizzard of entreaties that he endorse a fellow Republican before his home state votes, for example.)

But the Iowa senator has an altogether different attitude when it’s time to answer the call of the roll in the Senate — and he returned to the Capitol this week just after notching a monumentally difficult, and hardly noticed, record of perseverance.

After Tuesday evening, Grassley had not missed a recorded vote in 22 years, six months and six days. It’s now the longest temporal stretch of perfect attendance in senatorial history.

(Sean McMinn/CQ Roll Call)

Even he was unaware he’d actually broken that record last week, when he was on the losing end of a Jan. 12 vote that scuttled legislation mandating an audit the Federal Reserve.

“It’s pretty important for me to be able to quantify that I’m on the job, and I don’t know how else to do that when the Senate’s in session except not to miss a vote,” Grassley explained.

And during recess weeks he’s pursuing his commitment to visiting all 99 counties in Iowa, a goal he’s met in each of his 35 years as a senator. Presidential candidates who achieve that retail politicking feat boast of “doing the full Grassley.” Neither GOP senator in the top national polling tier has met that goal, while both Marco Rubio of Florida (121 missed votes as of last week) and Ted Cruz of Texas (82) have two of the lowest attendance records this Congress.

The previous mark for the longest period between missed Senate votes was set almost three decades ago. Wisconsin Democrat William Proxmire didn’t miss a ballot in the 22 years, five months and 28 days between April 20, 1966, and Oct. 18, 1988, when the roll was called for the final time before his retirement. (He died in 2005.)

What’s remarkably different about the two marathons, however, is the amount of formalized work involved

Grassley’s most recent vote, for confirming Minnesota Supreme Court Justice Wilhelmina Wright to the federal bench, was the 7,522nd ballot he’d cast without interruption — since July 14, 1993, when he missed four votes on a bill regulating political activity by federal employees. Instead, he spent that Wednesday back home, inspecting some of the worst flooding damage in Great Plains history with President Bill Clinton.

Proxmire went to the floor and gestured thumbs up or thumbs down 36 percent more often during his run, casting 10,252 votes in a row.

The dramatic difference over an essentially identical period of time reflects a reality of the modern Senate, lamented by Republicans and Democrats alike but especially by whichever party is in the minority and struggling to advance their ideas. Senators are not forced to say “aye” or “nay” to as many amendments, bills or confirmations as they once did. The number of recorded votes has averaged 297 annually over the past decade, a decline of 22 percent from the decade before.

At the current pace, Grassley would have to answer every call of the roll for the next nine years before breaking Proxmire’s iron man mark — meaning the 82-year-old Iowan , who’s currently a safe bet to secure his seventh term this fall, would have to come back for the start of yet another term in 2023.

“Let’s take one election at a time, I guess,” Grassley said, but “that probably means I’m never going to break the record by raw numbers.”

Now that the timing of almost every recorded vote is announced many hours in advance, and the balloting generally occurs between Tuesday afternoon and Thursday evening, it may be surprising only 17 senators had perfect attendance for 2015. (Twenty more missed only one or two votes.) But the vagaries of airline travel, illness and family emergency make keeping a streak going for decades a real rarity.

Only one other senator in history has cast more than 6,000 consecutive votes: Republican Susan Collins of Maine, who passed that mark in September and hasn’t missed a ballot since she took office in 1997.

But the truly astonishing mark for consistency in congressional attendance, a record that may stand at least as long as Cal Ripken’s for consecutive games played, was set two decades ago on the House side: Democratic Rep. William H. Natcher of Kentucky participated in 18,401 straight roll calls between his arrival in 1954 and the month before his death in 1994.

Grassley’s streak reflects the tenacity for which he’s been known throughout his long career, not only in advancing legislative goals (he’s been the top Judiciary Committee Republican since 2011 and before that held the party’s top seat on Finance for 10 years) but also in his beloved pursuit of oversight. Targets have ranged from the Pentagon to the Smithsonian Institution and from the Food and Drug Administration to the Nature Conservancy. Of late, he’s been on the case of such diverse targets as the Bureau of Prisons for dropping pork roast from its inmates’ menu, and Hillary Clinton confidante Huma Abedin on suspicions of misbehavior when she was a State Department official.

“That’s a much more important way of being tenacious,” he said, than simply showing up for work.